86o 



SIPHONAPTERA AND COLEOPTERA 



four Malpighian tubes. The intestine is divided into small intestine, colon, 

 and rectum, the last mentioned opening at the anus. 



The salivary apparatus is, as usual, separate from the alimentary canal. 

 It consists of two glands, on each side of the body, lying in the fat-body in 

 front of the stomach. The duct from each gland joins, forming a common 

 duct on each side, which runs forward to open into the salivary pump. This 

 is a hollow, chitinous organ, supplied with powerful muscles, situated at the 

 anterior end of the ventral surface of the hypopharynx. 



The duct of this pump, running forwards through the hypopharynx, opens 

 via the triradiate canal already mentioned as formed by the junction of the 

 hypopharynx with the mandibles, into the groove of these organs. 



The Act of Biting. — The flea apparently carefully selects the spot 

 at which it is to bite, and thenpierces ahole by means of thelabrum. 

 This hole is then enlarged by the mandibles, through whose grooves 



haemolyzed and digested. It appears that the black residual mass 

 is capable of further digestion by the rectal glands. Further 

 bionomics will be given under Xenopsylla cheopis. In some people 

 flea-bites may cause a local papular eruption — e.g., ceratophyllus 

 fasciatus. 



Life-History.— The egg is oval, waxy white or opaque porcelain in 

 appearance, smooth, and with a length of about 0-5 millimetre. 

 It is generally deposited between the hairs of the host, and falls 

 off on to the ground. In two to four days the larva is hatched. 

 This larva is an elongated worm-like little creature with fourteen 

 segments. The head is well developed, and has strong mandibles 

 suitable for biting. It lives on dead organic matter, and moults 

 three times as a rule — i.e., three to four days, and again six days, 

 and again seven to fourteen days after hatching. It then spins a 



4 



salivary secretion is 

 pumped into the skin. 

 This secretion irritates 

 the vessels, causing a 

 local rush of blood to 

 the part, and this blood 

 is drawn by the suction 

 of the pharynx up a tube 

 formed by articulation 

 of the labrum with the 

 mandibles. This tube, 

 of course, is embedded 

 in the skin, which is 

 pierced by its two com- 

 ponent parts. 



Fig. 452.— Egg of the Dog Flea. 

 (X50 Diameters.) 



(From a photograph by J. J. Bell.) 



There are therefore 

 two tubes in the mouth- 

 parts of a flea — an 

 efferent, carrying the 

 salivary secretion, and 

 an afferent, carrying the 

 blood, which is taken 

 to tlie stomach, and 



